Three-dimensional image-capturing apparatus

ABSTRACT

A three-dimensional image-capturing apparatus includes an image-capturing device having a plurality of image-capturing regions and a plurality of optical systems for forming images of a subject in the image-capturing regions. The optical systems includes a plurality of reflectors for reflecting rays from the subject a number of times and at least a lens provided to be closer to the image-capturing device than the reflection means closest to the subject. The reflectors and the lens are used to form, in the image-capturing regions, separate images of the subject which are captured from different viewpoints.

RELATED APPLICATION DATA

This application is a division of co-pending application Ser. No.11/140,210 filed May 27, 2005; and a continuation of Ser. No. 09/362,058filed Jul. 28, 1999, now abandoned. The present and foregoingapplications claim priority to Japanese Applications Nos. P10-217033filed Jul. 31, 1998, and P10-338708 filed Nov. 30, 1998. Each of theseapplications is incorporated herein by reference to the extent permittedby law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to three-dimensional image-capturingapparatuses, and in particular, to a three-dimensional image-capturingapparatus that obtains a three-dimensional image (stereo-image) bycapturing a plurality of images of the same subject which have parallaxand that determines the distance to the subject.

2. Description of the Related Art

For forming a three-dimensional image, a plurality of images obtained byviewing the same subject from a plurality of different points, that is,images having parallax, must be captured. Accordingly, in general, asingle three-dimensional image-capturing apparatus is provided with twocameras, and two images of a subject, viewed from two differentpositions, are captured by the two cameras.

The use of the two cameras increases the entire size of thethree-dimensional image-capturing apparatus, which causes a problem inthat the size cannot be reduced.

In the case where a three-dimensional image-capturing apparatus isconstructed using a plurality of separate camera units, the optical axesof the camera units must be aligned. However, it is very difficult toalign the optical axes of the separate camera units.

In the case where a three-dimensional image-capturing apparatus isprovided with a plurality of cameras, the cameras must be externallysynchronized for processing the picture signals. This inevitablyrequires a circuit for establishing synchronization, which causes anincrease in the price of the three-dimensional image-capturingapparatus.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide athree-dimensional image-capturing apparatus that uses a singleimage-capturing device to obtain a plurality of images having sufficientparallax, even though the image-capturing apparatus has a relativelysimplified structure and its size is small. The image-capturingapparatus is free from damage in that imaging lenses determining most ofoptical characteristics and performance are exposed from the apparatusto dust, etc.

To this end, according to an aspect of the present invention, theforegoing object is achieved through provision of a three-dimensionalimage-capturing apparatus including an image-capturing device having aplurality of image-capturing regions, and a plurality of optical systemsfor forming images of a subject in the image-capturing regions, theoptical systems including a plurality of reflectors for reflecting raysfrom the subject a number of times, and at least a lens provided to becloser to the image-capturing device than the closest reflectors to thesubject among the reflectors, wherein the reflectors and the lens areused to form, in the image-capturing regions, separate images of thesubject which are captured from different viewpoints having a distancetherebetween.

Preferably, the three-dimensional image-capturing apparatus furtherincludes a light-shielding unit provided at least between theimage-capturing device and the reflectors so as to separate the opticalsystems for forming images of the subject.

The three-dimensional image-capturing apparatus may further includelight-limiters provided to be closer to said subject than the reflectorsfor the (2n−1)-th reflection (where n represents a positive integer)from the image-capturing device along the optical systems, wherein thelight-limiters prevent incidence of flux of ambient light outer fromrays forming each image of the subject.

The three-dimensional image-capturing apparatus may further include asignal processor for dividing a video signal from the image-capturingdevice into video signals representing the images of the subjectcaptured in the image-capturing regions for capturing images of thesubject from the different viewpoints.

In the three-dimensional image-capturing apparatus, parallax which isthe distance between the viewpoints may be one centimeter or greater.

The image-capturing device may be a charge-coupled-device-typesolid-state image-sensing device or a metal-oxide-semiconductor-typesolid-state image-sensing device.

According to another aspect of the present invention, the foregoingobject is achieved through provision of a three-dimensionalimage-capturing apparatus including an image-capturing device, aplurality of imaging-side reflectors having reflecting surfaces providedto be obliquely outward for a plurality of different portions of theimage-capturing region of the image-capturing device, a plurality ofsubject-side reflectors having reflecting surfaces provided, for theimaging-side reflectors, outer from the imaging-side reflectors so as tobe oblique with respect to a subject, the subject-side reflectorsreflecting rays from a subject to the corresponding imaging-sidereflectors, a plurality of lenses or lens units provided to be closer tothe image-capturing device than the subject-side reflectors in opticalpaths formed from the subject to the different portions of theimage-capturing region of the image-capturing device so that rays fromthe subject are reflected by the subject-side reflectors and thereflected rays are further reflected by the imaging-side reflectors, thelenses or lens units forming a plurality of images of the subject whichhave parallax, and a plurality of diaphragms in which when each opticalpath has a lens, the diaphragms are provided to be closer to the subjectthan the lens and in which when each optical path has a lens unit, thediaphragms are provided to be closer to the subject than the lens unit.

The imaging-side reflectors and the subject-side reflectors may comprisemirrors, prisms, or what has a function of reflecting light.

The type of lens for imaging in each optical path may be a single lensor a set of at least two lenses.

The type of lens for imaging in the each optical path may be a sphericallens or an aspheric lens.

According to a further aspect of the present invention, the foregoingobject is achieved through provision of a stereo-camerarecording/reproducing system including a three-dimensionalimage-capturing apparatus including an image-capturing device having aplurality of image-capturing regions and a plurality of optical systemsfor forming images of a subject in the image-capturing regions, a singletiming generator for driving the three-dimensional image-capturingapparatus so as to output the images formed in the image-capturingregions in the form of a single video signal, a single driver, a camerasignal processor for implementing camera signal processing on the singlevideo signal, a single signal recorder for recording, on a singlerecording medium, the processed video signal output from the camerasignal processor, a single reproducer for reproducing the video signalrecorded on the recording medium, a video separating circuit forseparating the reproduced video signal from the reproducer into signalscorresponding to the image-capturing regions, and display apparatusesfor displaying the signals corresponding to the image-capturing regions,which are output from the video separating circuit, wherein the opticalsystems include a plurality of reflection means for reflecting rays fromthe subject a number of times and at least a lens provided to be closerto the image-capturing device than the reflectors closest to thesubject, and wherein the reflectors and the lens are used to form, inthe image-capturing regions, separate images of the subject which arecaptured from different viewpoints having a distance therebetween.

According to the present invention, a three-dimensional image-capturingapparatus requires a single image-capturing device. The singleimage-capturing device is used to obtain a plurality of captured imageshaving a different parallax, whereby the need for establishingsynchronization among a plurality of a plurality of cameras iseliminated. This further eliminates the need for providing a specialcircuit for establishing synchronization. By simply performing opticalaxis alignment for each optical system with respect to the sameimage-capturing device, required optical axis alignment is completed.Thus, optical axis alignment is facilitated compared with the case whereoptical axis alignment must be performed for a plurality of cameras. Inaddition, a possibility of damage in that imaging lenses determiningmost of optical characteristics and performance are exposed from theapparatus to dust, etc., can be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a three-dimensionalimage-capturing apparatus according to a first embodiment of the presentinvention;

FIGS. 2A and 2B are illustrations of the principles of capturingtwo-dimensional image, in which FIG. 2A shows that when the same subjectis captured from two viewpoints, two captured images of the subject areformed on different regions of an image-sensing device by opticalsystems and in which FIG. 2B shows the two captured images of the samesubject;

FIG. 3A is a schematic sectional view showing a three-dimensionalimage-capturing apparatus, and FIG. 3B is a block diagram showing anexample of a circuit for processing the output of the three-dimensionalimage-capturing apparatus shown in FIG. 3A;

FIG. 4 is a schematic sectional view showing a three-dimensionalimage-capturing apparatus according to a second embodiment of thepresent invention;

FIG. 5 is a schematic sectional view showing the principles ofperipheral flux cutting by a beam limiter in the second embodiment shownin FIG. 4;

FIGS. 6A, 6B, 6C, and 6D are schematic sectional views showingthree-dimensional image-capturing apparatuses according to otherembodiments of the present invention;

FIG. 7 is a block diagram showing a recording/reproducing system for athree-dimensional image-capturing apparatus; and

FIG. 8 is a block diagram showing a recording/reproducing system for athree-dimensional image-capturing apparatus.

DETAILED DESCRIPTION OF THE EMBODIMENT

Embodiments of the present invention are described below with referenceto the attached drawings.

FIG. 1 shows the structure of a three-dimensional image-capturingapparatus according to a first embodiment of the present invention. Thethree-dimensional image-capturing apparatus includes a solid-stateimage-sensing device 1, which has a half of the image sensing region ofthe image-sensing device 1 and the other half of the image sensingregion of the image-sensing device 1, an infrared-cut filter 2 providedin front of the image-sensing device 1, imaging lenses 3 a and 3 bprovided for the halves of the image sensing region via the infrared-cutfilter 2, diaphragms 4 a and 4 b provided corresponding to and in frontof the imaging lenses 3 a and 3 b, a pair of imaging-side mirrors 5 aand 5 b provided correspondingly to and in front of the diaphragms 4 aand 4 b so as to be directed in an obliquely outward direction, and apair of subject-side mirrors 6 a and 6 b provided correspondingly to andouter from the imaging-side mirrors 5 a and 5 b, which are directed inan obliquely inward direction. An optical shield unit 7 is providedbetween the imaging-side mirrors 5 a and 5 b and the image-sensingdevice 1. The optical shield unit 7 prevents optical cross talk betweenan imaging optical system formed by the imaging-side mirror 5 a, thediaphragm 4 a, the lens 3 a, and the half 1 a of the image sensingregion, and an imaging optical system formed by the imaging-side mirror5 b, the diaphragm 4 b, the lens 3 b, and the half 1 b of the imagesensing region The pair of subject-side mirrors 6 a and 6 b reflect raysfrom the same subject to the pair of imaging-side mirrors 5 a and 5 b atdifferent positions (the distance between the viewpoints, that is, theparallax is preferably, approximately 1 to 15 centimeters). The pair ofimaging-side mirrors 5 a and 5 b reflect the rays reflected by the pairof subject-side mirrors 6 a and 6 b to the halves 1 a and 1 b of theimage sensing region of the image-sensing device 1. The rays reflectedby the pair of subject-side mirrors 6 a and 6 b are controlled by thediaphragms 4 a and 4 b, and the controlled rays pass through the imaginglenses 3 a and 3 b to form images on the halves 1 a and 1 b of the imagesensing region. The controlled rays also pass through the infrared-cutfilter 2, whereby infrared radiation is cut off.

FIGS. 2A and 2B schematically illustrate the principles of capturing athree-dimensional image. FIG. 2A shows that when the same subject iscaptured from two different viewpoints at which the subject-side mirrors6 a and 6 b are positioned, two captured images of the subject areformed on the halves 1 a and 1 b of the image sensing region by theimaging-side mirrors 5 a and 5 b, the diaphragms 4 a and 4 b, and thelenses 3 a and 3 b. FIG. 2B shows the two images captured from thedifferent positions. From the comparison between the two captured imagesshown in FIG. 2B, it is found that the smaller cylinder and the pencilin front of the inmost cylinder are shifted in position. This is becausethe two captured images of the same subject have parallax. Accordingly,from the two captured images of the same subject which have parallax, astereo-image of the subject can be recognized.

In other words, by appropriately processing data representing theabove-described two captured images, and implementing image synthesis,three-dimensional recognition of the subject can be performed, and basedon the recognition results, the image of the subject can be reproducedin the form of a three-dimensional image. Obviously, the distance fromthe three-dimensional image-capturing apparatus to the subject can bedetermined. These functions are realized because the coordinates of theportions of the subject can be obtained by using the principles oftriangulation

FIG. 3A shows a three-dimensional image-capturing apparatus, and FIG. 3Bshows a block diagram of a circuit for processing the output of thethree-dimensional image-capturing apparatus shown in FIG. 3A. Two imagescaptured from the two viewpoints are obtained from an image-sensingdevice 1. A signal conversion circuit 8 converts video signalsrepresenting the images into the desired three-dimensional image data,and outputs them to the exterior. The output data are input to a displayunit (not shown) that can perform stereoscopic display, and arereproduced as a three-dimensional image.

By performing direct signal processing on the three-dimensionalinformation without separately processing the right and left images, andoutputting the processed data representing positional information on thesubject, the processed data may be used as image recognition data anddata representing the distance from the subject.

According to the three-dimensional image-capturing apparatus accordingto the first embodiment, two images of one subject are captured so as tohave parallax by the pairs of imaging optical systems composed of thesubject-side mirrors 6 a and 6 b, the imaging-side mirrors 5 a and 5 b,the lenses 3 a and 3 b, the diaphragms 4 a and 4 b, and the differentregions 1 a and 1 b of the image-sensing device 1. Thus, thethree-dimensional image-capturing apparatus requires a singleimage-sensing device. Since the image-sensing device 1 can obtain twocaptured images having a different parallax, the two cameras do not needto be synchronized with each other, which eliminates the need for usinga special circuit for synchronization.

By performing optical axis alignment for each optical system withrespect to the same image-sensing device, required optical axisalignment is completed. This facilitates the optical axis alignment,compared with the conventional case where optical axis alignment for twocameras is performed.

The subject-side mirrors 6 a and 6 b, which are used as a pair ofdiscrete viewpoints for obtaining two images having parallax, areprovided to be outer from the imaging-side mirrors 5 a and 5 b. Thisarrangement makes it possible to increase the distance between thesubject-side mirrors 6 a and 6 b, compared with the size of thethree-dimensional image-capturing apparatus. As a result, the parallaxcan relatively be increased. Therefore, a very stereo-image can beobtained at a relatively high precision.

In the above-described first embodiment, the subject-side mirrors 6 aand 6 b, and the imaging-side mirrors 5 a and 5 b, are used to reflectrays from the subject twice by an angle of 90 degrees, whereby the raysimpinge on the regions 1 a and 1 b of the image-sensing device 1.However, in order to reduce the depth size of the two optical systems inthe three-dimensional image-capturing apparatus, the rays from thesubject may be reflected twice by an angle (e.g., 120 degrees) greaterthan 90 degrees so as to be guided to the image-sensing device 1.

FIG. 4 shows a three-dimensional image-capturing apparatus according toa second embodiment of the present invention. The second embodiment hascomponents identical to those in the first embodiment. Detaileddescriptions of the identical components are omitted since the identicalcomponents have already been described. Only different components aredescribed, and in FIG. 4, the components identical to those in FIG. 1are denoted by the identical reference numerals.

Reflecting prisms 15 a and 15 b constituting imaging-side reflectingunits are provided in front of diaphragms 4 a and 4 b for the halves 1 aand 1 b of the image sensing region of an image-sensing device 1 so asto be directed in an obliquely outward direction. The reflecting prisms15 a and 15 b function identically as the imaging-side mirrors 5 a and 5b in the first embodiment—shown in FIG. 1.

Infrared-cut filters 16 a and 16 b are provided on the light-incidentside of the reflecting prisms 15 a and 15 b constituting theimaging-side reflecting units. In front of an image-sensing device 1, animage-sensor cover glass 17 is provided.

Light limiters 18 a and 18 b function to prevent incidence of raysexcluding rays to be incident on the image-sensing halves 1 a and 1 b ofthe image-sensing device 1. In other words, when rays excluding raysfrom imaging optical systems corresponding to the image-sensing halves 1a and 1 b are incident on the image-sensing halves 1 a and 1 b, theincident rays are noise components, which causes image-qualitydeterioration. Accordingly, the light limiters 18 a and 18 b preventflux of ambient light to leak.

FIG. 5 shows the principles of limitation of incident rays by a lightlimiter 18.

The rays from the subject pass through an imaging optical system to forman image on the image-sensing region of the image-sensing device 1, andrays surrounding rays contributing to imaging may become noisecomponents. In FIG. 5, an outermost ray A on the side of the subject isincident on the image-sensing device 1 at a greatest angle of incidence.Accordingly, rays outer from the ray A must be cut. For this purpose,the light limiter 18 may be provided for cutting rays outer from the rayA so—that the ray A passes the light limiter 18 before passing throughthe odd-numbered ((2n−1)-th where n represents a positive integer)reflecting unit from the image-sensing device 1, that is, the reflectingprism 15. This is because the provided light limiter 18 is positionedslightly to the central axis of the three-dimensional image-capturingapparatus so as to effectively prevent flux of ambient light to beincident. In other words, since the ray A is outside rays B and C, allfluxes of light caused by the rays A, B, and C can be allowed tocontribute to imaging without cutting the rays B and C.

In the case where the light limiter 18 is provided so that the ray Apasses through the light limiter 18 before passing through theodd-numbered (2n where n represents a positive integer) reflection unitfrom the image-sensing device 1, the flux of ambient light cannot be cutunless the light limiter 18 is provided outside the three-dimensionalimage-capturing apparatus. This disposition of the light limiter 18 isnot preferable because the size of the three-dimensional image-capturingapparatus cannot be reduced, and light shielding can effectively beperformed.

FIGS. 6A, 6B, 6C, and 6D show three-dimensional image-capturingapparatuses according to other embodiments of the present invention,respectively. Although the other embodiments have differences from thefirst and second embodiment shown in FIGS. 1 and 4, they have manycomponents identical to those in the first and second embodiments, andthe identical components have already been described. Accordingly, onlythe differences are described below.

The other embodiments shown in FIGS. 6A to 6D are different from thefirst embodiment shown in FIG. 1 in that two pairs of prisms 10 a and 10b, and 11 a and 11 b, are used as reflecting units instead of mirrors.The prisms 10 a and 10 b constitute subject-side reflecting units, andthe prisms 11 a and 11 b constitute imaging-side reflecting units. Byusing each prism as a reflecting unit, an advantage of facilepositioning is obtained in that by positioning the incident or emergentsurface of each prism to be parallel with or perpendicular to the imagesensing region or vertical direction of an image-sensing device 1, thereflecting surface of each prism can automatically be positioned at anangle of 45 degrees with respect to a subject or the image sensingregion of the image-sensing device 1.

In each of the three-dimensional image-capturing apparatus shown inFIGS. 6A and 6B, the number of lenses for each optical path is one, andlenses 4 a and 4 b are provided on the image-sensor side of diaphragms 3a and 3 b. In the embodiment shown in FIG. 6A, the diaphragms 3 a and 3b and the lenses 4 a and 4 b are provided between the prisms 10 a and 10b constituting the subject-side reflecting units and the prisms 11 a and11 b constituting the imaging-side reflecting units. In the embodimentshown in FIG. 6B, the diaphragms 3 a and 3 b and the lenses 4 a and 4 bare provided between the prisms 11 a and 11 b constituting theimaging-side reflecting units and the image-sensing device 1.

In each of the embodiments shown in FIGS. 6C and 6D, each optical pathis provided with a plurality of lenses 4 a, 4 b, 14 a, and 14 b. In theembodiment shown in FIG. 6C, diaphragms 3 a and 3 b, and the lenses 14 aand 14 b provided on the imaging side of the diaphragms 3 a and 3 b, areprovided between the prisms 10 a and 10 b constituting subject-sidereflecting units and the prisms 11 a and 11 b constituting imaging-sidereflecting units. The lenses 4 a and 4 b are provided between the prisms11 a and 11 b constituting imaging-side reflecting units and theimage-sensing device 1. In this arrangement, the lenses 4 a, 14 a, 4 b,and 14 b for the optical paths are positioned to be closer to theimage-sensing device 1 than the diaphragms 3 a and 3 b. Thus, the lenses4 a, 14 a, 4 b, and 14 b converge fluxes of light narrowed by thediaphragms 3 a and 3 b so as to form images. Accordingly, the size ofthe lenses 4 a and 4 b can be reduced.

In the embodiment shown in FIG. 6D, the positional relationships amongthe diaphragms 3 a and 3 b and the lenses 14 a and 14 b in theembodiment shown in FIG. 6C are reversed. The lenses 14 a and 14 bconverge rays before the rays are controlled by the diaphragms 3 a and 3b. However, the size of the lenses 4 a and 4 b can be reduced becausethe lenses 4 a and 4 b converge rays controlled by the diaphragms 3 aand 3 b.

In each of the embodiments shown in FIGS. 6A to 6D, an infrared-cutfilter is not provided, but may be provided. Instead of the opticalshield unit 7 shown in FIG. 1, the light limiters 18 a and 18 b in thesecond embodiment shown in FIG. 4 may be provided. Obviously, both theoptical shield unit 7 and the light limiters 18 a and 18 b may beprovided. Although an optical low-pass filter is not provided in theabove-described embodiments excluding the second embodiment, obviously,it may be provided. If the optical low-pass filter is provided, it maybe positioned at any position of each optical path. As described above,the present invention can variously be modified for practice.

An optimal mode for recording and reproduction by the above-describedthree-dimensional image-capturing apparatus is described below.

Two image-capturing regions 1 and 2 of a solid-state image-sensingdevice as used in the above-described three-dimensional image-capturingapparatus are driven by pulses generated from a common timing generator(TG), as shown in FIG. 7. Images formed in the two image-capturingregions are photoelectrically converted into electric signals, and theelectric signals are output from the image-sensing device. The electricsignals are supplied to a correlative double sampling (CDS) circuit andan auto-gain control (AGC) circuit. After the electric signals areconverted from analog to digital form, they are corrected by processessuch as auto-white balance, and the corrected signals are fed back tothe AGC circuit. As a result of the above-described camera signalprocessing, a video signal in which the video signals from the twoimage-capturing regions are simultaneously included are output from thecamera system. For example, the video signal can be output as a signalin accordance with the NTSC or PAL video signal format. Thus, recordingto a single recording medium by an ordinary videocassette recorder canbe performed. This makes it possible to use a single recording medium toperform simultaneous recording of signals from a plurality ofimage-capturing regions at a full frame rate.

The ordinary recording medium and the ordinary recording format can beused, whereby in the reproducing mode, a general video reproducer asshown in FIG. 8 is used, and simply adding an image-separating circuitto the output unit of the reproducer can separate a plurality of images.Accordingly, by simply inputting signals of the separated images fromthe image-capturing regions 1 and 2 into displays (display units 1 and2) capable of stereoscopic displaying, images having parallax can easilybe reproduced.

In order that a moving picture captured by a three-dimensionalimage-capturing apparatus may be recorded on a plurality of recordingmedia, and that the recorded picture may be reproduced, it is importantto establish synchronization among a plurality of recording apparatusesand among a plurality of reproducing apparatuses, which howevercomplicates the apparatuses. By using the three-dimensionalimage-capturing recording/reproducing system shown in FIGS. 7 and 8,video signals from two image-capturing regions can simultaneously berecorded as one signal on a single recording medium, and in thereproducing mode, the recorded signal including two signal components issimply reproduced. This eliminates the need for particularly using anexternal synchronizing circuit for establishing synchronization amongthe reproducing apparatuses.

1. A three-dimensional image-capturing apparatus comprising: animage-capturing device having a plurality of image-capturing regions;and a plurality of optical systems for forming images of a subject inthe image-capturing regions, the optical systems including (1) aplurality of reflection units which reflect rays from said subject anumber of times, (2) at least one lens provided to be closer to saidimage-capturing device than the closest reflection unit to said subject,and (3) a light-limiting unit provided between said plurality ofreflection units, wherein, at least one reflection unit is aimaging-side reflection unit located in front of the correspondingimage-capturing region and directed in an obliquely outward direction,at least one reflection unit a subject-side reflection unit locatedoutward from said imaging-side reflection unit and directed in anobliquely inward direction, the light-limiting unit is located closer tothe subject side reflection unit and is effective to only exclude rayscloser to the subject side reflection unit with a greatest angle ofincidence on the image sensing device, and said reflection unit and saidlens are used to form, in said image-capturing regions, separate imagesof said subject which are captured from different viewpoints having adistance therebetween.
 2. A three-dimensional image-capturing apparatusaccording to claim 1, wherein said light-limiting unit is providedcloser to the subject-side reflection unit than to the image-sidereflection unit.